C# Bot框架如何向确认对话框添加标题

我将按照此步骤构建聊天机器人

我的代码在Microsoft Bot Framework Emulator上运行良好，但在Facebook Messenger中测试时出现问题：

Is this your selection?
* Sandwich: Black Forest Ham
* Length: Six Inch
....
> no
What do you want to change? //Facebook Messenger stop and not display this line
 1. Sandwich(Black Forest Ham)
 2. Length(Six Inch)
> 2

下面是消息Bot框架：

{"error":{"message":"(#100) Param [elements][0][title] must be a non-empty UTF-8 encoded string","type":"OAuthException","code":100,"fbtrace_id":"HfCTxxxx"}}

我使用emulator进行调试，发现我的bot返回的内容标题为空

 "attachments": [
{
  "contentType": "application/vnd.microsoft.card.hero",
  "content": {
    "title": "",
    "text": "What do you want to change? ",
    "buttons": [

当用户键入

no

时，如何覆盖此卡

谢谢